It is well known to make polyalphaolefins by admixing an olefinic feed (1-hexene to 1-hexadecene) with a promoter and a catalyst, such as boron trifluoride (BF.sub.3), under mild pressure/temperature conditions. Polyalphaolefin product limitations, such as 100.degree. C. viscosity of less than 10 centistoke and oligomer distribution focused on the tetramer-hexamer fraction, arise from the use of the aforementioned processes. In general, higher viscosity fluids (100.degree. C. viscosity of greater than 10 centistoke) can only be made with a severe production rate penalty, since longer residence times are required to achieve the target viscosity with current technology.
U.S. Pat. No. 4,587,368 to Pratt et al. discloses the oligomerization of 1-alpha olefin in two stages to yield a mixture low in trimer and high in tetramer and higher oligomers. In the first stage, a C.sub.8-12 1-alpha olefin is oligomerised in a conventional process until the monomer is totally reacted. During that first stage, a BF3:promoter complex is formed. In the second stage, an aliquot of monomer is added and the reaction is allowed to go to completion. The final process yields a product viscosity of approximately 8 centistoke.
U.S. Pat. No. 4,982,026 to Karn et al. discloses highly reactive polymers obtained from low carbon number monomers. The process involves the preparation of a mixture of hexane solvent, phosphoric acid, and a catalyst substrate; cooling of mixture to -20.degree. C., and saturating the mixture with BF.sub.3 to form the catalyst complex. Propylene gas and BF.sub.3 are then added to complex until the reaction is completed (Example 1). In Example 2, a silica gel is used as a catalyst substrate with hexane solvent and phosphoric acid:BF.sub.3 complex components. Notice that the catalyst complex is a BF.sub.3 :acid complex, not a BF.sub.3 :alcohol complex. The process yields polymers with mole weights of from 250 to 500, having a high degree of mono-unsaturation content.
U.S. Pat. No. 4,650,917 to Dessau et al. discloses Viscosity Index improvers for synthetic lubricants produced by olefin oligomerization of olefin monomers by contact with BF.sub.3 solid acidic catalyst. The catalyst complex is a BF.sub.3 :silica complex, not a BF.sub.3 :alcohol complex. The Example describes the oligomerization of propylene over a BF.sub.3 -containing acidic resin catalyst and the subsequent isomerization of lube fraction by contact with an unbound hydrogen exchange zeolite.
U.S. Pat. No. 4,434,309 to Larkin et al. discloses the oligomerization of low molecular weight alpha olefins over a BF.sub.3 protonic promoter complex. Specifically, Example 10 describes the introduction of an alpha-olefin mixture to complex of BF.sub.3, 1-butanol, and cyclohexane, and the production low molecular weight synthetic lubricants. It appears that, in the examples using a BF.sub.3 protonic promoter complex, the oligomerization does not occur under boron trifluoride pressure.
U.S. Pat. No. 5,510,392 to Feuston et al. discloses the oligomerization of alpha olefins with a BF.sub.3 :promoter complex. The alpha olefins and the BF.sub.3 :promoter complex are added simultaneously to the reactor. The final product has a 100.degree. C. viscosity of 5.2 centistoke.
U.S. Pat. Nos. 4,434,309, 4,587,368, 4,650,917, 4,982,026, and 5,510,392 are hereby incorporated by reference for all purposes.